Monday 4 February 2013 11.44 EST
First published on Monday 4 February 2013 11.44 EST

A little after half past 12 on Monday, Justin Portal Welby stood beneath the dome of St Paul's Cathedral and promised, with the help of God, to "promote unity, peace, and love among all Christian people, especially among those whom you serve".

Twenty-five minutes later, with the arcane and archaic legalities duly addressed, the final decree porrected and any opposition to the election declared contumacious, the 57-year-old former oil executive was confirmed as the 105th archbishop of Canterbury, in the presence of several senior bishops.

As the leader of the 77 million members of the worldwide Anglican communion, Welby now finds himself presiding over a church facing two pressing and divisive issues: the government's same-sex marriage proposals and the Church of England's failure last November to vote for the introduction of female bishops. Although the new archbishop supports the official C of E position that marriage is defined "as being between a man and a woman", he, like his predecessor, Rowan Williams, voted in favour of the consecration of female bishops.

"I stand, as I have always stood over the last few months, with the statement I made at the announcement of my appointment, which is that I support the Church of England's position on this."

The new archbishop, a father of five, said that while he was looking forward to the job, he could not help feeling "very challenged and very awed by it".

"It is an enormous privilege and my experience is to trust in the grace of God, not in your own abilities," he said.

Asked how he and his family were settling into Lambeth Palace, the former bishop of Durham joked that they were "getting lost".

Given the challenges ahead, the readings at St Paul's were apt in the extreme.

"The patient in spirit are better than the proud in spirit," ran the text from Ecclesiastes. "Do not be quick to anger, for anger lodges in the bosom of fools. Do not say: 'Why were the former days better than these?' For it is not from wisdom that you ask this."

More pertinent still were the exhortations from the second letter of Timothy: "Proclaim the message; be persistent whether the time is favourable or unfavourable; convince, rebuke, and encourage, with the utmost patience in teaching. For the time is coming when people will not put up with sound doctrine, but having itching ears, they will accumulate for themselves teachers to suit their own desires, and will turn away from listening to the truth and wander away to myths."

The readings were followed by a sermon from John Sentamu, the archbishop of York, in which he attacked "the most self-regarding culture in many centuries"; a culture in which "the phones are smart", but few people are wise, and in which fast cars are fetishised by those too seduced by speed to contemplate the view through the window.

"Never was a culture so written in the first person singular," he said. "In the words of the late George Harrison, 'I me mine'."

In a separate statement welcoming the confirmation, Sentamu described Welby as a man who was "outspoken in the pursuit of justice, and unafraid to grapple with complex issues", adding: "I call upon everyone in the Church of England, and in the wider Anglican communion, especially those in the global south, to spend time with God on their knees, bringing Bishop Justin, Caroline and their children before him and asking that he be given wisdom, courage and the grace of Jesus Christ."

Welby will be enthroned at a service in Canterbury Cathedral on 21 March.